This invention relates in general to imaging, and more specifically, to an improved imaging system.
There has been recently developed a photoelectrosolographic imaging system capable of producing high quality images of high density, continuous tone, and high resolution. This system is described and claimed in the above mentioned copending application Ser. No. 403,002. In a typical embodiment of this imaging system, a photoelectrosolographic structure comprising a conducting substrate with a layer of softenable or soluble material, containing photosensitive particles overlying the conductive substrate is imaged in the following manner: An electrostatic latent image is formed on the photoconductive surface, e.g., by uniform electrostatic charging and exposure to a pattern of activating electromagnetic radiation. The softenable layer is then developed by exposing the plate to a solvent which dissolves only the soluble layer. The photoconductive particles which have been exposed to radiation migrate through the softenable layer as it is softened and dissolved, leaving an image on the conductive substrate conforming to a negative of the original. This is known as a positive to negative image. Through the use of various techniques, either positive to positive or positive to negative images may be made depending on the materials used and the charging polarities. Those portions of the photoconductive layer which do not migrate to the conductive substrate may be washed away by the solvent with the softenable layer.
In another recently developed imaging system, an image is formed by the selective disruption of a particulate material overlying an electrostatically deformable film or layer. The imaging structure used in this system is substantially the same as that used in a photoelectrosolographic imaging already described above, and involves exposing the charged member to an optical image to selectively relocate the charge and form a developable charge pattern. The softenable layer is then developed or softened by heat whereupon the particulate layer is selectively disrupted resulting in a rearrangement of the particles to form an image viewable by reflected or transmitted light. When the structure is developed by heat, the photoconductive area or layer is disrupted and the photoconductive particles are thereby selectively rearranged to change the optical properties of the plate. The image is believed to be formed because the photoconductive particles drift on top of one another and accumulate in valleys or pockets of the deformation image leaving the raised portions of the image uncovered. This imaging system is believed to be substantially due to a surface disruption effect with no substantial migration of the photoconductive particles within the softenable layer. This final image differs from that of photoelectrosolography described above, in that the softenable layer is deformed in conjunction with a disruption of the photoconductive particles. This system is described and claimed in copending application Ser. No. 520,423, filed on Jan. 13, 1966, now abandoned.
Another related imaging system is directed to the formation of a photoelectrosolographic image, and comprises exposing a photoelectrosolographic structure to a vapor to form a migration image, composed of photoconductive particles followed by heating said structure, whereby a high density image having a low background is produced. This system is described and claimed in copending application Ser. No. 612,122, filed on Jan. 27, 1967. If desired, the migration image formed above may be utilized as a separate image without resorting to the heating step.
In general, three basic migration imaging member structures may be used: a layered configuration which comprises a conductive substrate coated with a layer of softenable material, and an overcoating of photoconductive material (usually particulate) embedded at the upper surface of the softenable layer; a binder structure in which the photoconductive particles are dispersed throughout the softenable layer which overcoats a conducting substrate; and an overcoated structure in which a conductive substrate is overcoated with a layer of softenable material followed by an overcoating of photoconductive particles and a second overcoating of softenable material which sandwiches the photoconductive particles.
The photoelectrosolographic process comprises a combination of process steps which include charging, exposing, and developing with a solvent. The characteristics of these images are dependent on such process parameters as potential, exposure, and development time, as well as the particular combination of the process steps. High density, continuous tone and high resolution are some of the photographic characteristics possbile. The image is characterized as a fixed or unfixed photoconductivee powder image which can be used in a number of applications such as microfilm, hard copy, optical masks, and stripout applications using adhesive materials. Alternative embodiments of this concept are further described in the above cited copending applications.
In a related imaging system described in copending U.S. Pat. application Ser. No. 483,675, filed Aug. 30, 1965, now U.S. Pat. No. 3,909,963, non-photoconducting particulate material is used to form images in the photoelectrosolographic mode already defined above. In this system, a developable image is formed by charging in image configuration through the use of a mask or stencil. This image is then developed in a solvent for the softenable material.
Although each of the above imaging systems is capable of producing excellent images, the structure being imaged includes a conductive support member which functions as a ground plane during the development or migration of the photoconductive particles during the development step. The elimination of the conductive support would greatly simplify the manufacture of such structures and significantly reduce their cost.